Wireless testing firm RootMetrics said AT&T edged out Verizon Wireless in the early results of its latest study, which were made available to CNET. It's a surprise call because Root had routinely crowned Verizon as the top carrier.

The study was based on a combination of speed and reliability. Verizon has long held a leadership position in reliability and continues to do so in the most recent results. But AT&T has narrowed the gap considerably, which allows its speed advantage to put it over the top.

The test, which began in July and tested 60 markets, is only about halfway done and will be completed during the course of the year. The results, characterized as a horse race by RootMetrics CEO Bill Moore, may differ when wrapped up.

Still, these kinds of kudos are increasingly important as the carriers seek ways to stand out from each other. With most of the carriers moving to the same high-speed cellular technologies, and offerings many of the same high-profile smartphones, network quality is a critical selling point.

The competitive environment has resulted in what amounts to a billion-dollar shouting match between the carriers, as each strives to tout the quality of their service. AT&T set off another war of words in July by proclaiming itself the nation's fastest and most reliable network, nabbing away the reliability claim from Verizon.

AT&T based the claim off of another study conducted by Nielsen. Verizon, however, maintains that it is the most reliable network.

"We've always been about reliability," said a Verizon representative. "It's about needing to get on the network and staying on the network."

AT&T, unsurprisingly, was pleased with the early results.

"AT&T has the nation's fastest and most reliable 4G LTE network," said a company representative. "As the saying goes, 'it's not bragging if you can back it up.'"

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AT&T's turnaround AT&T edging out Verizon marks a huge reversal for the carrier, which has long struggled with issues with network coverage and reliability. The problems were at their worst when AT&T had the exclusive rights to the iPhone and was overwhelmed by the deluge of traffic it brought.

Customers mocked the carrier -- with good reason -- and forced AT&T to move quickly to improve its network.

While AT&T still faces a perception issue with its network, the recent studies reflect the work and money the company has put in to improving its network. Moore said AT&T has moved up right behind Verizon in terms of reliability -- an unthinkable scenario even a few years ago.

Even as RootMetrics had Verizon as the overall leader in the first half, AT&T had gained ground, Moore said.

A number of recent studies showing the speed of its network have emboldened AT&T to pour money into a campaign touting superiority over rival Verizon. The Nielsen study had only convinced AT&T to push even harder.

Moore said he saw marked improvement from AT&T in the last few months. He said the call failure rate fell by 60 percent from a year ago, while data reliability improved.

RootMetrics sheds some light The release of the new data by RootMetrics is an attempt by the firm to shed additional light on the shadowy world of cellular tests, whose methods aren't often disclosed, as well as better define the terms "reliability" and "speed," two words that are used a liberally.

Verizon still claims a more reliable network.
Verizon

"What we're trying to do is put a stake in the ground and challenge the industry," said Moore.

Moore's point: cellular technology and services have evolved over the past decade and a half, and testing processes need to evolve with it.

"15 years ago, we were just happy that these phones worked," he said.

Reliability, for instance, used to be about whether a phone could get a signal -- any signal. But RootMetrics defines it simply as being able to do "what you want to do, when you want to do it, without interruption," holding carriers to a higher standing. For Root, reliability applies to calls, data, and text messages.

For speed, RootMetrics goes beyond testing peak speeds, and looks practically at how quickly a person can accomplish a task on a smartphone. Moore noted that some carriers with a higher peak speed actually have slower task completion times.

The results, which the firm is posting on its Web site, will include a RootScore that combines the two factors. But for the first time, the firm will also break out the individual speed and reliability scores.

The other major carriers, Sprint and T-Mobile, continued to lag behind the bigger players, particularly when it came to reliability, Moore said.

But he noted both of the smaller carriers have made significant improvements, and touted T-Mobile's non-LTE network, which runs on a technology called HSPA+, as the fastest network behind LTE.

Ultimately, Moore said he is releasing more details on the scores and definition of wireless jargon to get the process out in the open, which he believes will educate consumers and result in better network improvements.

"We're holding ourselves to a transparent standard," Moore said. "We want to be under the microscope."

Updated at 12:54 p.m. PT: to include the name of the firm that found AT&T to be the most reliable network.